1. Field of the Invention
This invention relates to vacuum cleaners and the removal of accumulated dust on the filter element during operation of the vacuum cleaner. More specifically, the invention relates to a valve system for creating or inducing reverse pulses of air through the filter element in order to shake and drive collected dust from the filter element.
2. Description of the Prior Art
Vacuum cleaners and in particular commercial scale vacuum cleaners involving a large tank wherein filter elements in the form of fabric bags or sleeves inserted in or mounted to a plate which divides the tank into two chambers are well known and commonly used. Dust-laden air is directed into one of two chambers and is filtered as it is drawn through the filter elements into the other dust-free chamber by the action of an exhauster attached to the clean air containing chamber. Periodically the accumulated dust on the filter elements must be removed by shaking or reversing the direction of air flow through the filter elements. Various methods have been proposed to accomplish this task including disassembling the cleaner tank and physically shaking the filters to elaborate systems for injecting compressed gas through the filters.
In U.S. Pat. No. 3,008,542 a pair of squirrel cage blowers direct the dust-laden air through the blowers into a set of valved pipes and then to a dust removal stage. By virtue of switching these valves the air flow was reversed for removal of dust deposits. In contrast, U.S. Pat. No. 3,680,285 discloses a tubular filter bag-type cleaner wherein a flushing system with external pilot-controlled, pressure-activated diaphragms having rows of ejector tubes, one for each bag, is employed to discharge pressurized air in addition to a back-flow of air from the clean air section to remove dust. Similarly, in U.S. Pat. No. 3,765,152, reverse flow of air through filter bags in order to maintain permeability of the porous filter media is accomplished by a gas distribution system which injects a jet of compressed air through venturi tubes that project into each bag. In U.S. Pat. No. 4,007,026 a method of creating air pulses to clean filter cartridges without venturi tubes is disclosed involving a compressed gas manifold suspended over the openings in the filter cartridges with an orifice directed at each opening. For further references and details of a multitude of various prior art devices see U.S. Pat. No. 4,007,026 which is herein incorporated by reference for that purpose.
In U.S. Pat. No. 3,653,190 an apparatus for reversing the direction of air flow through the fabric filter bags which shakes the dust from the bags is disclosed wherein a pair of synchronized valves are employed to close the inlet side of the exhauster and open the clean air side of the filter bags into the atmosphere. This system requires extraordinary force to actuate valves large enough to accomplish this task particularly in commercial scale vacuum cleaners. The present invention deals with this type of system and is considered an improvement thereof.